Coolant Temperature Sensor/Switch (For Computer): Description and Operation

Engine Coolant Temperature (ECT) Sensor







The engine coolant temperature (ECT) sensor checks the temperature of the engine coolant. The temperature of the engine coolant is required so that the engine control module (ECM) can regulate:
- the injection period
- the idle speed
- the engine cooling fan (FC)
- the ignition advance
- engagement and disengagement of the A/C compressor
- diagnostic functions.

The sensor is a negative temperature coefficient (NTC) type which is supplied with power from the control module (signal) and is grounded in the control module.

The resistance in the sensor changes depending on the temperature of the coolant. Depending on the resistance in the sensor, a voltage (signal) is transmitted to the Engine Control Module (ECM). At 0 degree C, the voltage is approximately 4.0 V. At 100 degree C the voltage is approximately 0.5 V. Low temperature results in high voltage (high resistance), high temperature in low voltage (low resistance).

The engine coolant temperature (ECT) sensor is located beside the thermostat.

The engine control module (ECM) can diagnose the engine coolant temperature (ECT) sensor. The sensor value can be read off using VADIS/VIDA.